Weird HSD behaviour

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by ald1stil1, Mar 2, 2026 at 6:47 PM.

  1. ald1stil1

    ald1stil1 New Member

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    Hello everyone and greets from Italy.

    I've recently started to notice an unusual behaviour in the energy monitor on the screen of my 2008 Prius.
    I bought it in December 2024 but since then there was nothing to report about the hybrid system, until now.
    Basically, as far as my experience with this car, there is always energy coming back and forth from the battery, but in my case it happens only when regenarating/recharging.
    It all began almost right after I installed and Android stereo with CarPlay, with a preassembled wire harness and a small resistor for steering wheel aircon control retain. As soon as I noticed this issue I swapped the new radio with the original one but nothing changed.
    Then I checked the secret menu in the car and found some errors but apparently all related to the stereo swap and nothing else.
    I also checked the 12v battery voltage but it looks good even with the car off.
    Honestly, I don't know what to do at this point, and I really hope that it's not about the HV battery modules.
    Attached here are some pictures and screenshots (sorry for the italian).
    I have some videos but cannot post any link since I don't have enough message history at the moment.

    Thanks in advance for any help!
     

    Attached Files:

    #1 ald1stil1, Mar 2, 2026 at 6:47 PM
  2. Tombukt2

    Tombukt2 Senior Member

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    Yes I think you're going to be opening that HV battery it needs attention .
     
    #2 Tombukt2, Mar 3, 2026 at 12:59 PM
  3. ald1stil1

    ald1stil1 New Member

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    I really hope it won't be necessary..

    Here are a couple of videos i took while driving:

    Energy meter 1
    Energy meter 2
    Dr Prius app
     
    #3 ald1stil1, Mar 3, 2026 at 2:09 PM
  4. Brian1954

    Brian1954 Senior Member

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    I watched the Dr Prius video, and everything looks normal to me. There is no need to be concerned about hybrid battery. Everything is working like it should. Just drive the car. If there is a problem with the hybrid battery, you will get warning lights on the dashboard.
     
    #4 Brian1954, Mar 3, 2026 at 6:17 PM
  5. Hayslayer

    Hayslayer Active Member

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    Considering your battery is sitting at >65% state of charge and you're still charging it at 50-70 amps, I would say.....stop charging it, it doesn't want to be at that high of an SOC. Normally it stays between 62ish% and 42ish%
     
    #5 Hayslayer, Mar 3, 2026 at 6:29 PM
  6. dolj

    dolj Senior Member

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    I’m not sure what you’re getting at here. The OP is driving the car and has no control over how the battery ECU determines when and how much current to send to the battery. If you’re assuming the OP was force‑charging it, again, the battery ECU will only permit what it deems safe. You cannot charge the battery to more than 80% SoC this way.
    From my viewing of your two videos, I did not see this behaviour. It looked very normal to me given the speeds you were driving. I would have liked to see a stretch at a steady speed (say 45 kph and 70 kph) on cruise control, just to see what it would do there. Your videos showed a lot of acceleration and deceleration while driving, but the short stretch at 82 kph at the very end of the second video looked good.

    Your Dr Prius screenshot showed some values higher than I would like to see when the battery was charging, but otherwise it all looked normal. I have no idea whether that voltage is within the acceptable range, as I have never made such observations on my own car. Most importantly, the voltage difference never exceeded 0.12 V between the highest and lowest blocks.
     
    #6 dolj, Mar 3, 2026 at 9:30 PM
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